This invention relates to a method and apparatus for transforming thermal energy from a geothermal heat source consisting of a mixture of geothermal liquid and geothermal steam ("geofluid" ) into electric power. This invention further relates to utilizing the energy potential of both geothermal liquid and geothermal steam in one integrated system.
Geothermal heat sources can generally be divided into two groups. In the first group are "liquid-dominated" heat sources that produce mostly hot geothermal liquid (brine). In the second group are "steam-dominated" heat sources that produce mostly geothermal steam with some geothermal liquid.
Methods for converting the thermal energy released by geothermal heat sources into electric power present an important and growing area of energy generation. Geothermal power plants generally belong to one of two categories, namely, steam plants and binary plants.
In steam plants, the geothermal source is utilized directly to produce steam (e.g., by throttling and flashing geothermal liquid). That steam is then expanded in a turbine, producing power. In binary plants, heat extracted from the geothermal liquid is used to evaporate a working fluid that circulates within the power cycle. The working fluid is then expanded in a turbine, producing power.
Steam plants are generally used for steam-dominated geothermal heat sources, while binary plants are generally used for liquid-dominated geothermal heat sources. U.S. Pat. No. 4,982,568 describes a method and apparatus for transforming thermal energy from geothermal liquid into electrical power in a binary plant. This method increases efficiency by using a thermodynamic cycle with a multi-component working fluid and internal recuperation.